The present invention relates to resonant drivers. More specifically, the present invention relates to resonant drivers providing periodic electronic signals with low power dissipation. Further, the present invention relates to methods for automatically tuning of resonant drivers. Further, the present invention relates to resonant display drivers and methods for operating resonant display drivers in liquid crystal displays. Further, the present invention relates to resonant digital to analog converters and methods of operation.
Resonant drivers are part of a family of circuit designs that are used to provide periodic electronic signals with low power dissipation. This area of technology is also termed harmonic driving, adiabatic charging or switching. Typical applications for such resonant drivers include generating and distributing of clock signals for computer displays, for memory chips, for microprocessors, etc. Resonant drivers typically include LRC portions that are characterized by resonant frequencies. When the resonant frequency of an LRC portion of a resonant driver matches the frequency of the periodic signal being driven, the power required to provide the periodic signals is significantly reduced.
Practical problems with the implementation of resonant drivers include that the resonant frequency is highly dependent upon the actual values of capacitive and inductive elements used. Although capacitors and inductors include "nominal" values, the "actual" values of these elements vary significantly from batch to batch, supplier to supplier, and component by component. Causes of these variations include variations in manufacturing precisions, variations in temperature, variation in load, variations in quality of materials, etc. Because of these variations, a resonant driver will have an output frequency that typically is different from the resonant frequency the resonant driver is designed to operate at. As a result of this difference, the amount of power saved by the addition of resonant drivers is small.
As a result of the above problems, current methods for constructing and tuning of resonant drivers are manually performed. For example, the capacitive, inductive, and resistive loads of a load circuit must first be manually characterized, and then specific capacitive and inductive elements of an LRC portion must then be manually selected so as to obtain the desired resonant frequency. Such inefficiencies inhibit the use of resonant drivers in a wide variety of applications.
What is needed are improved resonant driver circuits and tuning methods.
Liquid crystal displays (LCDs) are displays that are used to display analog or digital data from computers, television signals, etc. LCDs operate by establishing particular voltages across pixel on the display, with the particular voltage affecting the optical properties of the LC material. Voltages are typically applied to each pixel on the display by using a row conductor and column conductors. Because row and column conductors are relatively long and highly capacitive, charging and discharging of these conductors and pixels dissipates a substantial amount of energy. The amount of power dissipated is significant because current refresh rates of display pixels are at rates of up to 120 MHz. In general, the power dissipation of conductors is given by the expression: EQU power dissipation=frequency*capacitance of the wire*(voltage).sup.2
Previous techniques for reducing power dissipation have concentrated on reducing the capacitance and the voltage, with limited success. However, what is required are improved methods and apparatus for further reducing power dissipation of liquid crystal displays.
Digital to analog converters (DACs) are typically used to convert digital values to analog voltages. In a typical DAC, a voltage source is provided for generating the analog output voltage, in response to a digital value. Because DACs typically drive highly capacitive loads, the power required for supplying typical DACs is large.
What is required are improved methods and apparatus for reducing power dissipation of digital to analog converters.